Digital cameras using an image sensor generally are capable of exposure control using image data read by the image sensor. However, because the image data are read after the flash exposure during flash photography, light adjusting control cannot be performed during the flash emission using the read image data.
Conventionally, the following light adjusting control methods are often used. One light adjusting control method is an external light adjusting control method wherein flash exposure light reflected from a photographic subject is received by an external light adjusting control element without passing through a photographic lens, so as to control the flash exposure based on the output signals from this external light adjusting control element. Another light adjusting control method performs a preliminary flash exposure prior to a main flash exposure, and controls the main flash exposure based on the image data from an image sensing element during the preliminary flash exposure.
In the case of the former light adjusting control method, since the light reflected from the photographic subject does not pass through the photographic lens, a shift may be generated in the light adjusting control range relative to changes in the field angle accompanying dislocation of the lens position as when a zoom lens is used as the taking lens. This shift in the light adjusting control range may be directly and disadvantageously linked to a shift in the light adjusting control precision. In the case of the latter light adjusting control method, there is no concern of a shift in the light adjusting control range caused by change in field angle because the flash exposure light reflected by the photographic subject passes through the taking lens. However, a time lag may be disadvantageously generated in the light adjusting control because a flash exposure must be performed twice, once in the preliminary flash exposure and once in the main flash exposure.
Another well-known light adjusting control method separate from the above mentioned methods controls luminance and is a method wherein light reflected from a photographic subject and passing through a photographic lens is reflected by the photoreceptor surface of the image sensor, and this reflected light is received by a separately provided photoreceptor element which measures the amount of reflected light received to accomplish light adjusting control. In this instance, however, the degree of precise flatness of the photoreceptor surface of the image sensor is readily affected by the material forming the photoreceptor surface, e.g., metal, protective glass and the like, such that light adjusting control data does not have a high reliability.
An object of the present invention is to eliminate the previously described disadvantages by providing a digital camera capable of highly reliable light adjusting control in real time without fear of dislocation of the light adjusting control range due to change of field angle during flash photography.